1. Field of the Invention
The present invention relates generally to a method and apparatus for Bit Resolution Enhancement (BRE) and edge enhancement in an electronic device. The present invention relates particularly to a method and apparatus for enhancing a bit resolution and eliminating a contour noise and simultaneously, enhancing an edge of an image (i.e., a contour) in an electronic device.
2. Description of the Related Art
Typical techniques for enhancing a quality of an image include a Bit Resolution Enhancement (BRE) technique and an edge enhancement technique. The BRE technique eliminates a high frequency component, which is expressed as a contour due to a decrease of the number of bits of an image, using a Low Pass Filter (LPF). The edge enhancement technique enhances a high frequency component of an image.
In general, if the number of bits expressing a one-dimensional signal decreases, a discontinuous point is generated. The discontinuous point appears as an unnecessary high-frequency component. FIGS. 1A and 1B are graphs illustrating one-dimensional signals depending on number of bits. For example, as shown in FIGS. 1A and 1B, a continuous signal expressed at 8 bits appears as a discontinuous signal at 6 bits. In the case of a two dimensional image, the discontinuous signal is expressed as an artifact called a contour. The BRE technique restores a decreased number of bits to the original state in order to eliminate the contour. As above, the contour expressed as the discontinuous signal is eliminated using the LPF. FIG. 2 is a diagram illustrating a general 5×5 mask. For example, a contour can be eliminated by applying an LPF of Equation (1) below to a center pixel value (Y13) in a 5×5 mask of FIG. 3.
                    Y_out        =                              ∑                          k              =              0                        24                    ⁢                                    Y              k                        ⁢                          /                        ⁢            25                                              (        1        )            
In Equation (1), ‘Yk’ represents a pixel value of an image corresponding to Ykth of the 5×5 mask, and ‘Y_out’ represents an output pixel value of an LPF of the 5×5 mask format.
In general, if the BRE technique is applied to an image, a contour noise is not reduced, but a portion of the image corresponding to an edge is affected and flattened. Thus, according to the conventional art, the BRE technique is applied to increase a quality of an image and then, the edge enhancement technique is applied to restore an edge flattened due to the BRE to the original state.
For the edge enhancement, there a variety of methods are provided. Among the provided methods, the most basic method can be expressed in Equation (2) below:
                    output        =                              Y            ⁢                                                  ⁢            13            ×            2                    -                                                    Y                ⁢                                                                  ⁢                7                            +                              Y                ⁢                                                                  ⁢                8                            +                              Y                ⁢                                                                  ⁢                9                            +                              Y                ⁢                                                                  ⁢                12                            +                              Y                ⁢                                                                  ⁢                14                            +                              Y                ⁢                                                                  ⁢                17                            ⁢                                                          +                              Y                ⁢                                                                  ⁢                18                            +                              Y                ⁢                                                                  ⁢                19                                      8                                              (        2        )            
Equation (2) represents a technique for enhancing an edge by subtracting an average value of pixels around a center pixel (Y13) from double the center pixel value in the 5×5 mask of FIG. 2.
In the conventional art, the BRE technique and edge enhancement technique are independently researched and provided respectively and thus, the edge enhancement technique is separately applied after the BRE. However, a method of applying the two techniques respectively as described requires adding a line memory at the time of hardware implementation and thus, causes a problem of an increased cost.